Different headers or footers for odd and even pages in MS Word
It is easy to have different content in your headers or footers for odd and even pages, e.g. to make page numbers appear at the left corner for even pages and at the right corner for odd pages. Double click a header (or footer) to start editing it, and go the “Design” menu to check the option “Different Odd and Even Pages”. Now edit any header of an odd page and any header of an even page to create different content for odd and even pages.
However, you may face this seemingly strange behavior when you try to create your content. Changing something, e.g. paragraph alignment, in your odd header, changes it also in the even header, although you have selected the option for “Different Odd and Even Pages”!
Most probably your problem comes from the style that you use in your header or footer. Normally this style is called “header” (or “footer”). You need to find it (in the “Home” menu) and modify it. In the first card that appears when you click “Modify”, make sure that the option “Automatically update” is unchecked.
Automatic update means that any change you make in a header is passed to the style, and thus it is applied universally, to odd and even headers alike. When you clear this option headers will keep all features defined already, but any changes you make in a header from that moment on will be regarding only the specific header type, odd or even.